1. Field of the Invention
The present invention relates to a printer which records or prints using an ink ribbon.
2. Description of the Prior Art
A full-line thermal head uses a full-line head which has heating elements along the entire recording width of a recording paper sheet. The head applies heat on an ink ribbon having the same width as itself, thereby performing thermal printing. During such a printing process, the ink ribbon and the recording paper sheet are fed at the same speed by separate drive sources so that they are fed at the same pitch.
However, it is difficult to feed the ink ribbon and the recording paper sheet in complete synchronism with each other. For example, during the initial stage of the feeding operation, one of the ink ribbon and the recording paper sheets cannot be immediately fed. Furthermore, in the stop operation, one of three ink ribbons and the recording paper sheet cannot be stopped. When these two members cannot be fed in synchronism with each other, this alone may not provide any adverse effect. However, if the two members are urged against each other by means of the thermal head, the paper sheet may be contaminated with the ink. Furthermore, if the recording paper sheet and the ink ribbon are fed by separate drive sources, the overall structure becomes complex.
In a serial thermal printer wherein a thermal head is urged against a recording paper sheet through an ink ribbon and a carriage is moved to perform printing, a ribbon cassette for feeding the ink ribbon is mounted on the carriage. The ink ribbon must be wound up at the same speed in synchronism with the movement of the thermal head, and hence, the movement of the carriage. For this purpose, a transmission shaft for transmitting the ribbon winding power is mounted on the carriage. However, in a conventional printer of this type, the up-down movement of the thermal head (swing movement between a printing position at which the head is urged against the paper sheet through the ink ribbon and a non-printing position at which the head is separate-d from the paper sheet) for paper feeding (or line feed) is controlled by a separate drive source from that for the winding operation of the ink ribbon. For this reason, the upward movement of the thermal head and the winding stop of the ink ribbon cannot be completely synchronized with each other. In addition, the downward movement of the thermal head and the feeding operation of the ink ribbon cannot be completely synchronized with each other either. Therefore, when the thermal head must be fed without printing with the thermal head in the up position, the ink ribbon is fed but is not used for printing, or the ink ribbon and the paper sheet may be urged against each other to contaminate the recording surface of the paper sheet.
When the thermal head is moved while the ink ribbon is stopped, the ink ribbon may be damaged, or the recording surface of the paper sheet may be contaminated since the head is urged against the recording paper sheet. Furthermore, separate drive sources (motor or the like) are required for up-down movement of the thermal head and the winding operation of the ink ribbon so that the overall printer becomes complex in structure and high in manufacturing cost.